Show an inclination to be a cad (4)

I believe the answer is:

heel

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'a cad' is the definition.
('heel' can be a synonym of 'cad')

I don't understand how the remainder of the clue works.

(Other definitions for heel that I've seen before include "3's weak point" , "that may be Cuban" , "A cad and a bounder!" , "Crusty end of a loaf" , "swine" .)

I've seen this clue in the Evening Standard.

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